The carbon Alpenhorns I've seen have been beautifully made. And amazingly light, of course. One of @Cycliste's colleagues plays one, but has to play it in the hall of the block of flats he lives in because none of the rooms in his flat are big enough, IIRC. Must have very understanding neighbours.
Or why not go for a carbon fibre one...a steal at CHF 3700
http://swisscarbonalphorn.net/en/acheter/